ABSTRACT
ROTEN, RORY LUCAS. Evaluation of Woody Vegetation and Loblolly Pine Responses to Aminocyclopyrachlor. (Under the direction of Drs. Rob Richardson, David Jordan, and David Monks).
Aminocyclopyrachlor is a new auxin mimicking active ingredient from DuPont Crop Protection and is currently registered for use in many non-cropland settings because of its broad spectrum control of many hardwood and broadleaf weed species. Much laboratory and field work was conducted between 2007 and 2011 to evaluate the efficacy of
aminocyclopyrachlor for cut-stump application, site preparation for loblolly pine production, and to determine the absorption and translocation within loblolly pine. For cut –stem,
ailanthus was controlled between 88 and 100% with all treatments regardless of rate 12 months after treatment (MAT). All aminocyclopyrachlor treatments controlled sweetgum between 43 and 55%, while triclopyr-bee controlled sweetgum 84%. Height and stem counts were also lowest with triclopyr-bee. Black locust control was best with triclopyr-bee (10%) plus imazapyr (1%) at 96%. Height and stem counts were also lowest at this rate. Based upon these results, aminocyclopyrachlor applied as a cut stem treatment effectively
aminocyclopyrachlor may be of use for site preparation, however more research is needed. It was determined in the absorption and translocation study that only 37% of the
aminocyclopyrachlor free acid was absorbed when foliar applied. However, absorption was very rapid, plateauing after only an hour. No significant difference was found in translocation regardless of harvest interval; 59% of the free acid remained within the treated needle and fascicle, 27% in the upper stem section, and all other parts had significantly less
Evaluation of Woody Vegetation and Loblolly Pine Responses to Aminocyclopyrachlor
by Rory Roten
A thesis submitted to the Graduate Faculty of North Carolina State University
in partial fulfillment of the requirements for the degree of
Master of Science
Crop Science
Raleigh, North Carolina 2011
APPROVED BY:
_______________________________ Dr. Rob J. Richardson
Committee Chair
________________________________ ________________________________
ii BIOGRAPHY
Rory Lucas Roten, the firstborn child of Roger and Ronda Roten, was born New Year’s Day 1985, the third baby of the year at Forsyth Medical Center. Having experienced a nomadic childhood, he now regards Danbury, North Carolina, a small country town located in Stokes County, as home. He enjoys everything outdoors including camping, backpacking, hunting, snowboarding, and controlling the world’s weed populations.
Having commenced his collegiate career at North Carolina Agricultural and Technical State University, he transferred to North Carolina State University in the fall of 2005; here, he completed his Bachelor of Science in Agricultural Extension and Education. While trying to gain funds for an international school-sponsored trip, Rory was
introduced to Dr. Rob Richardson and was hired as an undergraduate research assistant in January 2006. More than five years later, he is currently a research associate for Dr. Richardson, performing in a job where he is able to do what he ultimately loves: teaching.
iii ACKNOWLEDGMENTS
iv TABLE OF CONTENTS
LIST OF TABLES ...v
LIST OF FIGURES ...vi
CHAPTER I: Literature Review Abstract ...1
Vegetation Management ...1
Cut Stump ...3
Site Preparation ...4
Auxin Mimicking Herbicides and Related 14C Studies ...6
Aminocyclopyrachlor ...8
Literature Cited ...10
CHAPTER II: Aminocyclopyrachlor Cut Stem Application Efficacy on Selected Woody Species Abstract ...17
Introduction ...18
Materials and Methods ...20
Results and Discussion ...21
Literature Cited ...24
CHAPTER III: Aminocyclopyrachlor Efficacy for the Site Preparation of Loblolly Pines (Pinus taeda) Abstract ...31
Introduction ...32
Materials and Methods ...34
Results and Discussion ...35
Literature Cited ...39
CHAPTER IV: Absorption, Translocation, and Metabolism of Aminocyclopyrachlor in Loblolly Pine (Pinus taeda) Abstract ...48
Introduction ...49
Materials and Methods ...51
Results and Discussion ...55
Sources of Materials ...58
v LIST OF TABLES
Chapter I
Table 1.1 Aminocyclopyrachlor compared to like chemistries ...16 Chapter II
Table 2.1 Percent control, height, and stem count one year after cut-stem application for ailanthus, black locust, and sweetgum ...30 Chapter III
Table 3.1 Evaluation of loblolly pine site preparation treatments with
aminocyclopyrachlor and industry standards for hardwood control and pine response from 2008 trials at one year after treatment ...44
Table 3.2 Evaluation of loblolly pine site preparation treatments with
aminocyclopyrachlor and industry standards for hardwood control and pine response from 2008 trials at one year after treatment ...45 Table 3.3 Pine injury, survival, and height data pooled over treatments and segregated by month at one and two years after treatment ...46 Table 3.4 Weather data indicating the average daily temperature, wind gust, and minimum temperature at the three planting times ...47 Chapter IV
vi LIST OF FIGURES
Chapter I
Figure 1.1 Chemical structures of aminocyclopyrachlor free acid and ester,
aminopyralid, clopyralid, and picloram ...15 Chapter II
Figure 2.1 Distribution of sweetgum and black locust ...28 Figure 2.2 Chemical structures of aminocyclopyrachlor free acid and
aminocyclopyrachlor ester ...29 Chapter III
Figure 3.1 Native range of loblolly pine ...43 Chapter IV
1 Chapter I
Literature Review
Abstract
Aminocyclopyrachlor is an auxin mimic herbicide in development by DuPont Crop
Protection since 2003. This new compound is the first herbicide in the pyrimidine carboxylic acid family and has both soil and foliar activity on many problematic woody and vine
species. It has been evaluated for use in turf and several non-cropland areas (i.e. bareground, rights-of-way, and range and pasture). The objective of this chapter is to give an overview of aminocyclopyrachlor for: vegetation management, cut stump application, site preparation, absorption, translocation, and metabolism.
Vegetation Management
2 Several common methods exist in which vegetation can be controlled including cultural, biological, mechanical, chemical, and mixtures thereof. These methods can include hand cutting, mowing, and herbicide application (Jackson and Finley 2007; Johnstone 2008). Common herbicide application methods in non-cropland include, but are not limited to: basal bark, basal soil, cut stump, foliar, hack and squirt, and stem injection. Decisions about
herbicide(s) selection and application methods can be made easier by appropriate scouting and problem identification. Variables such as soil type, plant species presence, density and size, timing of application, and weather should all be taken into consideration in order to obtain desirable control (Jackson and Finley 2007; Nickerson 1991). In regards to application decisions, work by Nowak et al. (1992) indicates that cost effectiveness of treatments can be determined by density and height of undesirables. If a stand is dense but short, a foliar application would be more economically feasible, but in the event of low density and increased heights, a more selective basal application would be better.
3 preventable tree related instances (Hurysz and Crider 2008). In the occurrence of wildfire, conductors must be de-energized for safety precaution because carbon particles in smoke can conduct electricity. This situation can in turn emulate a lightning bolt of 500,000 volts (Johnstone 2008).
Cut Stump
Many woody species produce stump sprouts including black locust (Robinia pseudoacacia), red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), yellow poplar (Liriodendron tulipifera), and various other species. Stump sprouts are a common occurrence in areas such as a clear cut where woody species are mechanically cut at harvest and hardwood stumps are left. One method that works well to combat such a problem is a cut stump application (Haymond and McNabb 1994). One major advantage to this technique is that it works on invasive hardwoods and woody vine species of various sizes with the exception of stems less 1.27 cm (0.5 in). Application is simplistic, however can be labor intensive. A stem should be cut between 2.54 and 15.24 cm and treated as soon as possible to ensure rapid translocation through the phloem. Also, if a stem is cut at the upper limit, a future cut stump application can be made if not first successful (Enloe et al. 2010).
4 application to avoid off target injury. Herbicides that contain 2,4-D, dicamba, and picloram can be exuded from treated stump roots and injure nearby susceptible plants. This is known as “flashback”. (Schalau 2006)
Site Preparation
Over ten thousand products are made from wood and over one-half of harvested timber is utilized towards heating fuel (Young et al. 2003). Also, within the last century, much more agricultural land has been left fallow or converted and is being utilized for timber production (Zhao et al. 2008). Zhao et al. (2008), also explain that because of urban sprawl, the
increasing demand of timber is not easily supplied due to the loss of usable land. Due to such a high demand, new tactics must be looked upon to meet goals and provide the world the needed timber (Martin and Jokela 2004). However, after timber is harvested, it is the principle goal of silviculture to replant seedlings or prepare a location for natural regeneration so that a steady supply is always accessible (Young et al. 2003).
5 efficiently. Issues that influence site preparation decisions should include an estimate of productivity through a site index, costs, and amount of inputs after replanting. (Hamilton 1995)
Nilsson and Allen (2003), describe long term effects of site preparation. Most site
preparation treatments that rely on herbicides typically follow the trend which has fast initial growth response that plateaus with no subsequent increase of production. In the event that the herbicidal treatment ward off competing vegetation, another response can be seen with great initial growth gains and subsequent increases throughout the rotation, All of which can be influenced by many factors including soil conditions and tree bedding. By double bedding, a further decrease of competitive vegetation can be seen and as a result increase transplant heights. However, by double bedding, one is only increasing the volume of timber to the site and not increasing the volume per tree. Double bedding does provide a potential ability to thin a stand which consequently assists in the growth of the standing trees while promoting resistance to insects and disease (Jackson and Finley 2007).
6 Auxin Mimicking Herbicides and Related 14C Studies
Auxin, deriving from the Greek meaning “to grow” was the first plant hormone discovered beginning in 1880 with Charles Darwin. Much later in the 1930’s the hormone was named indole-3-acetic acid (IAA) (Paciorek and Friml 2006). Later yet, the auxin mimicking mode of action (MOA) was simultaneously discovered in 1941 in the United Kingdom and the United states with the independent development of MCPA and 2,4-D (Cobb and Reade 2010). Not only is this chemistry one of the oldest, it is also one of the most widely used with over 1,500 formulated products with this MOA (Ware 1983). Kelley and Riechers (2007), also make note of these chemicals’ popularity due to the lack of resistance issues. For instance, there are over 150 weed biotypes resistant to acetolactate synthase inhibitors and triazine herbicides compared to only 40 biotypes resistant to the auxin type herbicides
regardless of its widespread usage. Furthermore, due to the anatomical differences in grasses’ vascular structure and the difference of metabolic rate, auxinic herbicides have little to no effect on monocotyledons (Kelly and Riechers 2007). This observance held true until the relatively new advent of the quinolinecarboxylic acids; quinclorac does show activity on grass weeds. (Grossmann 2000)
Though auxin mimicking herbicides are widely used and have proven to be advantageous, little is known about how they work. It is understood that the application of an auxinic herbicide causes a chain of events to occur. With the accumulation of IAA,
7 that the auxin MOA is known. Consequently, this scheme also stimulates the production of abscisic acid (ABA) biosynthesis which is channeled throughout the plant closing stomata and increasing biomass. This cycle which affects cell division and expansion is what, in fact, kills the plant. (Grossmann 2000)
With such a great amount of interest in these compounds, a vast amount of research has occurred to trace chemicals throughout a plant in order to better understand the chemical (i.e. how much is absorbed, where it moves, and how or if it is metabolized). Carbon-14 (14C) is a radioactive isotope of carbon that is naturally occurring and relatively safe (Anonymous 2005). 14C synthesized pesticides enables one to gain much knowledge because it is traceable within the plant much like barium would be used in a medical realm (Anonymous, 2007).
8 Aminocyclopyrachlor
Aminocyclopyrachlor has been under development since 2003 by DuPont Crop Protection. It has been evaluated for use in various non-cropland areas such as airports, farmyards,
highways, and wildlife areas, any of which may be on military, private, or public lands. With its broad-spectrum, broadleaf weed control, aminocyclopyrachlor has a potential to control many glyphosate, acetolactate synthase (ALS), and triazine resistant weeds (Anonymous 2009; Bukun 2010).
Currently, there are three forms of the active ingredient: the potassium salt, the methyl ester formulation (DPX-KJM44), and the free acid (DPX-MAT28). Bukun et al. (2010) reported that aminocyclopyrachlor is active on many species including those in the Asteraceae, Chenolpodiaceae, Convolvulaceae, Euphorbiaceae, Fabaceae, and Solanaceae families.
Aminocyclopyrachlor is the first herbicide in the pyrimidine carboxylic acid family and is an auxin mimicking herbicide causing an epinastic response due a disruption in gene expression (Rossi, 2010). With the exception of an additional nitrogen atom (Figure 1), the structure of aminocyclopyrachlor is similar to aminopyralid, clopyralid, and picloram, all of which are auxin mimic herbicides. (Bukun et al. 2010; Strachan et al. 2010).
9 (solubility). The ester formulation has a higher, positive log Kow, which means greater
lipophilicity (Bukun et al., 2010). Strachan et al. (2010) also note that the free acid of aminocyclopyrachlor does not readily volatilize like its methyl ester counterpart. In their research, it was found that respectively 80% was lost due to volatility when applied with 1% methylated seed oil (MSO) after 192 hours.
Currently, only one aminocyclopyrachlor product is registered as a standalone herbicide (Imprelis™, a potassium salt formulation). It was approved August 31, 2010 and registered
for use in turf. Three more herbicides (Perpspective®, Streamline™, and Viewpoint™) were registered in December 2010 for non-cropland uses including vegetation management, bareground, and selective weeding. However, only the turf product is an
aminocyclopyrachlor stand-alone product whereas the non-cropland herbicides include MAT28 plus one or more of the following: chlorsulfuron, metsulfuron methyl, and/or imazapyr (Ferrell and Sellers 2009; Lindenmayer et al. 2010; Yeiser 2010).
Lastly, one primary benefit to aminocyclopyrachlor is the favorable environmental profile. In comparison to two of the standards in Table 1, the methyl ester formulation has a
10 Literature Cited
Anonymous, 2005. Human health fact sheet. Argonne National Laboratory. Available Online: http://www.ead.anl.gov/pub/doc/carbon14.pdf. Access: 11 January 2011. Anonymous, 2006. University of Maryland Medical Center. Available Online:
http://www.umm.edu/cgi-bin. Accessed: 11 January 2011.
Anonymous, 2009. DuPont™ DPX-MAT28 technical bulletin. DuPont Crop Protection. Bukun, B., Gains, T.A., Nissen, S.J., Westra, P., Brunk, G., Shaner, D.L., Sleugh, B.B.,
Peterson, V.F. 2009. Aminopyralid and clopyralid absorption and translocation in Canada Thistle (Circium arvense). Weed Sci. 57: 10-15.
Bukun, B.,Lindenmayer, R.B., Nissen, S.J., Westra, P., Shaner, D.L., and Brunk, G. 2010. Absorption and translocation of aminocyclopyrachlor and aminocyclopyrachlor-methyl ester in Canada Thistle (Cirsium arvense). Weed Sci. 58: 96-102.
Cobb, A.H. and Reade, P.H. 2010. Herbicides and plant physiology. Second Edition. Wiley-Blackwell. United Kingdom.
Devine, M.D. and Vanden Born, W.H. 1985. Absorption, translocation, and foliar activity of clopyralid and chlorsulfuron in Canada Thistle (Cirsium arvense) and Perennial Sowthistle (Sonchus arvensis). Weed Science. 33: 524-530.
Enloe, S., Loewenstein, N., Cain, D. 2010. Cut stump herbicide treatment for invasive plants in pastures, natural areas, and forests. Agronomy and Soils Series, Timely
Information. Alabama Cooperative Extension System.
11 http://conference.ifas.ufl.edu/aw10/presentations/Wed/Session%20B/1340%20Ferrell
.pdf. Accessed: 2 January 2011.
Grossmann, K. 2000. Mode of action of auxin herbicides: a new ending to a long, drawn out story. Trends in Plant Science. 5(12):506-8.
Haagsma, T. 1975. Dowco 290 herbicide – a coming new selective herbicide. Down Earth. 30: 1-2.
Hamilton, R. 1995. Reforestation as an investment: does it pay? Woodland Owner Notes. North Carolina State University Cooperative Extension. Available Online:
http://www.ces.ncsu.edu/nreos/forest/woodland/won-ob.thml. Accessed: 21 April
2010.
Haymond, J.L., McNabb, K. 1994. Southern hardwood management. Southern Region Cooperative Extension Services Management Bulletin. pp 45-50.
Hurysz, P. and Crider, J. 2009. Technology advances vegetation management. Transmission and Distribution World; ROW Management. October: 48-54.
Jackson, D.R. and Finley, J.C. 2007. Herbicide and forest vegetation management. Pennsylvania State University. College of Agricultural Sciences, Agricultural Research, and Cooperative Extension.
Johnstone, R. 2008. Integrated vegetation management. Utility Arborist Association (UAA) Quarterly. Summer: 5-17.
12 the Society of Range Management and Weed Science Society of America in Denver, CO.
Kelley, K.B. and Riechers, D.E. 2007. Recent developments in auxin biology and new opportunities for auxinic herbicide research. Pesticide Biochemisty and Physiology. 89: 1-11.
Martin, T.A. and Jokela, E.J. 2004. Stand development and production dynamics of loblolly pine under a range of cultural treatments in north-central Florida USA. Forest Ecology and Management. 192: 39-58.
McBroom, M.W., Beasley, R.S., Chang, M. and Ice G.G. 2008. Storm runoff and sediment losses from forest clearcutting and stand re-establishment with best management practices in east Texas, USA. Hydro. Process. 22: 1509-1522.
McWhorter, M. Olsen, J.K., University of Florida, Potter, M.F., and Knapp, F.W. 2010. Mosquitoes. Urban integrated pest management in the southern region.
Minkel, J.R., 2008. The 2003 northeast blackout—five years later. Scientific America. Available Online: http://www.scientificamerican.com/article.cfm?id=2003-blackout-five-years-later. Accessed: 4 August 2011.
Nanita, S.C., Pentz A.M., Grant, J., Vogl, E., Devine, T.J., and Henze, R.M. 2009. Mass spectrometric assessment and analytical methods for quantitation of the new herbicide aminocyclopyrachlor and its methyl analogue in soil and water. Anal. Chem. 81: 797-808.
13 Niering, W.A. and Goodwin, R.H. 1974. Creation of relatively stable shrublands with
herbicides: arresting “succession” on rights-of-way and pastureland. Ecology. 55: 784-795.
Nilsson, U. and Allen H.L. 2003. Short- and long-term effects of site preparation, fertilization and vegetation control on growth and stand development of planted loblolly pine. Forest Ecology and Management. 175: 367-377.
Nowak, C.A., Abrahamson, L.P., Neuhauser, E.F. Forebank, C.G., Freed, H.D., Shaheen, S.B., and Stevens, C. H.. 1992. Cost effective vegetation management on a recently cleared electric transmission line right-of-way. Weed Tech. 6: 828-837.
Paciorek, T. and Friml, J. 2006. Auxin signaling. Journal of Cell Science. 119: 1199-1202. Rossi, L. 2010. Proposed registration of aminocyclopyrachlor on non-crop areas, sod farms,
and residential lawns. U.S. Environmental Protection Agency, Office of Pesticide Programs Registration Division.
Schalau, J. 2006. Cut stump application of herbicides to manage woody vegetation. The University of Arizona Cooperative Extension. Bulliton no.: AZ1401.
Senseman, S.A. 2007. Herbicide Handbook 9th Edition. Lawrence, KS: Weed Science Society of America.
Strachan, S.D., Casini, M.S. Heldreth, K.M., Scocas, J.A., Nissen, S.J., Bukun, B., Lindenmayer, R.B., Shaner, D.L., Westra, P. and Brunk, G. Vapor movement of synthetic auxin herbicides: aminocyclopyrachlor, aminocyclopyrachlor-methyl ester, dicamba, and aminopyralid. Weed Sci. 58: 103-108.
14 Wilson, B.F. 1968. Red maple stump Sprouts: development the first year. Harvard Forest
Paper. 18: 1-10.
Wood, A. 2010. Compendium of pesticide common names. Available Online: http://www.alanwood.net/pesticides/index.html. Accessed: 1 January 2011.
Yeiser, J. 2010. Screening MAT28 for cut stump control of yaupon, sweetgum, and Chinese tallowtree. Abstract O-309 in Proceedings of the Society of Range Management and Weed Science Society of America in Denver, CO.
Young, R.A. and Giese, R.L. 2003. Introduction to forest ecosystem science and management. Third Edition.
15
A)
B)
C)
D)
E)
16 Table 1.1. Aminocyclopyrachlor compared to like chemistries (Anonymous 2009; Senseman 2007).
DPX-KJM44 Triclopyr-tea 2,4-D-dma Imazapyr-IPA
Soil half-life 37 to 128 days 10 to 46 days 7 to 28 days 25 to 142 days
Koc 28 mL/g 20 mL/g 20 mL/g --
Photodegradation Rapid Rapid Minor Minor
Solubility 4.2 g/L 2,100 g/L 796 g/L 11.3g/L
17 Chapter II
Aminocyclopyrachlor Cut Stem Application Efficacy on Selected Woody Species
Abstract
Field studies were conducted to determine the response of sweetgum (Liquidambar
styraciflua), black locust (Robinia pseudoacacia), and ailanthus (Ailanthus altissima) to the methyl-ester formulation of aminocyclopyrachlor. These species are prone to stump
sprouting and can be problematic in rights-of-way, range, and pasture settings. Treatments included aminocyclopryachlor at rates of 2.5, 5, 10, and 15% v/v as well as triclopyr-butoxyethyl ester (triclopyr-bee) (30% v/v), triclopyr-bee (10%) plus imazapyr (1%), and triclopyr-bee (20%) plus imazapyr (1%) applied by hand with a foam paint brush
immediately after cutting the stem between 5 and 13 cm above soil level. Remaining solution volume was filled with a commercial grade basal bark oil. Ailanthus was controlled between 88 and 100% with all treatments regardless of rate 12 months after treatment.
18 Introduction
Ailanthus [Ailanthus altissima (Mill.) Swingle], black locust (Robinia pseudoacacia L.), and sweetgum (Liquidambar styraciflua L.) are common species in the Eastern U.S. and are weedy in many non-cropland sites throughout the southeastern United States (Little 2006). Although sweetgum and black locust are native to this region (Figure 1), ailanthus is shown to be quite invasive outside of its native habitat of China (Ingo 1995). Similarly, all three species can regenerate prolifically through either root or stump sprouting from adventitious buds at or below ground level. Furthermore, these species are known to share root systems causing a complexity of problems in terms of herbicidal treatments whereas chemicals may travel and harm nearby vegetation even when treated plant(s) died (Haymond and McNabb 1994; Leonard and Murphy 1965; Schalau 2006). These traits decrease the value of timber, prohibit efficient growth of high value timber species, and can become hazardous if not controlled (Hamilton 1995; Siso and Burzycki 2004).
19 Senseman 2007; Shalau 2006; Siso and Buzycki 2004). Herbicides that contain dicamba, imazapyr, picloram, and 2,4-D can be can cause flashback, the exudation of herbicide from treated stump roots and injure nearby susceptible plants (Schalau 2006; Haymond and McNabb 1994).
Auxin mimicks are the one of the oldest chemistries in terms of herbicides with over 1,500 formulated products (Ware 1983). They are desirable for use partly due their efficacy and selective control for broadleaf weeds as well as the lack of resistance issues (Kelley and Riechers 2007). Although auxin mimic herbicides are widely used and have proven to be advantageous, little is known about how they work. It is understood that the application of an auxinic herbicide causes a chain of events to occur. With the accumulation of IAA,
1-aminocyclopropane- 1 -carboxylic acid (ACC) synthase is inhibited followed by ethylene production. The over production of ethylene, in turn, causes the epinastic response that the auxin MOA is known for. Consequently, this scheme also stimulates the production of abscisic acid (ABA) biosynthesis which is channeled throughout the plant closing stomata and increasing biomass. This cycle which affects cell division and expansion is what, in fact, kills the plant. (Grossmann 2000)
20 the coupling of basal bark application and cut stem application in the event that the vessels have sealed (Enloe et al. 2010; Leonard and Murphy 1965).
Similarly to triclopyr-bee, DuPont (Wilmington, Delaware) has introduced a new herbicide with the common name, aminocyclopyrachlor. This herbicide is also an auxin mimic type herbicide and has been formulated into ester and free acid forms. The ester formulation, DPX-KJM44 (KJM) has an attached methyl group and is more volatile in comparison to the free acid form, DPX-MAT28 (Figure 2) (Bukun et al. 2010; Strachan et al. 2010; Wood 2010). To date, little information has been published about KJM efficacy when applied as a cut stump treatment. Therefore, research was conducted to assess the efficacy of
aminocyclopyrachlor on selected woody species and regeneration of these species when treated with various rates of KJM in comparison to standard commercial treatments of triclopyr-bee, and triclopyr-bee plus imazapyr.
Materials and Methods
Individual trials were conducted in 2008 and 2009 with ailanthus, black locust, and
21 treatments were applied within five minutes of cutting to ensure maximum phloem
translocation.
All treatments were hand applied to the entirety of the cut surface using a specifically designated foam or bristled paint brush. Experimental treatments included the soluble liquid formulation of DPX-KJM44 at 2.5, 5, 10, and 15% v/v. For comparison purposes, industry standard treatments of triclopyr-bee (30% v/v), triclopyr-bee (10% v/v) plus imazapyr (1% v/v), and triclopyr-bee (20% v/v) plus imazapyr (1% v/v) were also included. Remaining solution volume was filled with commercial basal bark oil (Hy-Grade I™, CSC Chemical INC., Cloverdale, VA).
Sites were rated at eight (data not shown) and twelve months after treatment (MAT) for percent control on a 0 to 100% scale (0% being no plant injury and 100% being complete plant death), re-growth, and average height per plot. Data from individual species were tested for homogeneity using Levene’s test of equality of variance and subjected to analysis of variance using SAS Proc GLM (SAS 2004) and Fisher’s Protected LSD at P ≤ 0.05.
Results and Discussion
22 while 79% of their untreated cut stumps re-sprouted, all chemical treatments resulted in less than 21% sprouting. While we expected to have good control with triclopyr and/or imazapyr treatments, KJM was equally affective with 91 to 94% control 12 MAT.
Black locust control at 12 MAT was best (96%) with triclopyr-bee (10%) plus imazapyr (1%) at 96% control (Table 1). Statistically this treatment was only different from the two low rates of KJM alone. Black locust height was lowest after treatment with triclopyr-bee (10%) plus imazapyr (1%) at 18 cm. Height of regrowth following aminocyclopyrachlor
application ranged from 124 to 203 cm. Stem counts were 0.1 to 0.5 per plot with treatments containing triclopyr-bee, but was not different from stem count of 1.6 with 15% v/v
aminocyclopyrachlor.
At 12 MAT, sweetgum was (87%) controlled more effectively when triclopyr-bee when applied at 30% v/v (Table 1). Aminocyclopyrachlor controlled sweetgum less than
commercially desired (46 to 57%) with no differences between treatments. Sweetgum height and stems count were lowest following triclopyr-bee treatment at 5 cm and 1.56 stems per plot on average, but did not differ from the triclopyr-bee plus imazapyr treatments. Height and stem counts following KJM treatments did not differ from the nontreated control.
23 penetrant as a basal bark application controlled black locust and sweetgum 81 to 86% with a 91 to 92% reduction in height. While aminocyclopyrachlor is chemically similar to
24 Literature Cited
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Leonard, O.A. and Murphy, A.H. 1965. Relationship between herbicide movement and stump sprouting. Weeds. 13:26-29.
Little, E.L., 2006. Digital representations of tree species range maps from "Atlas of United States Trees". USGS. Available Online: http://esp.cr.usgs.gov/data/atlas/little/. Accessed on: 1 February 2011.
McLemore, B. F. and Cain, M. D. 1988. A test of basal sprays for controlling hardwood brush and trees. In: Environmental legislation and its effect on weed science: Proceedings, 41st annual meeting Southern. Weed Science Soc; 1988 January 18-20; Tulsa, OK. Volume 41.
Miller, James H. 1990. Streamline basal application of herbicide for small-stem hardwood control. Southern Journal of Applied Forestry. 14(4): 161-165.
26 Schalau, J. 2006. Cut stump application of herbicides to manage woody vegetation. The
University of Arizona Cooperative Extension. Available Online:
http://ag.arizona.edu/pubs/garden/az1401.pdf. Accessed: 11 December 2010.
Sellers, B.A., Langeland, K.A., Ferrell, J.A., Meisenberg, and Walter, J. 2010. Identificaiton and control of Coral Arisia (Ardisia crenata): A Potentially Poisonous Plant.
University of Florida Extension. Available
Online:http://edis.ifas.ufl.edu/pdffiles/AG/AG28100.pdf. Accessed: 3 February 2011. Siso, C.L., Burzycki, G.M. 2004. Survival of Shoebutton Arisia (Ardisia elliptica) in forested
wetlands after cut-stump treatments with Ttriclopyr. Weed Technology. 18: 1422-1426.
Shaner, D.L. 1988. Absorption and translocation of imazapyr in Imperata cylindrical (L.), raeushel and effects on growth and water use. Tropical Pest Management. 34: 388-392.
Strachan, S.D., Casini, M.S. Heldreth, K.M., Scocas, J.A., Nissen, S.J., Bukun, B.,
Lindenmayer, R.B., Shaner, D.L., Westra, P. and Brunk, G. 2010. Vapor movement of synthetic auxin herbicides: aminocyclopyrachlor, aminocyclopyrachlor-methyl sster, dicamba, and aminopyralid. Weed Sci. 58: 103-108.
27 Zedaker, S.M., Lewis, J.B., Smith, D.W., Kreh, R.E. 1987. Impact of season of harvest and
29
A) B)
31 Ch apter III
Evaluation of Aminocyclopyrachlor Efficacy for Loblolly Pine (Pinus taeda) Site Preparation
Abstract
A field study was conducted to evaluate efficacy of two aminocyclopyrachlor formulations in comparison to a standard treatment of imazapyr for site preparation prior to loblolly pine transplanting. Aminocyclopyrachlor formulations included the methyl ester DPX-KJM44 (KJM44) and the acid DPX-MAT28 (MAT28). Experimental treatments included MAT28 (64 to 256 gm ai ha-1), MAT28 or KJM44 (71 gm ai ha-1) plus sulfometuron methyl (212 gm ai ha-1) plus metsulfuron methyl (71 gm ai ha-1), and MAT28 or KJM44 (256 gm ai ha-1) plus sulfometuron methyl (212 gm ai ha-1) plus metsulfuron methyl (71 gm ai ha-1). For
comparison, a standard treatment of imazapyr (566 gm ai ha-1) plus sulfometuron methyl (212 g, ai ha-1) plus metsulfuron methyl (71 gm ai ha-1) was applied. Bare root pine seedlings were transplanted at three, four, and five months after treatment (MAT) to evaluate the effect of time after chemical treatment. Injury to transplanted pine was observed and was different injury between years (12 to 23% injury in 2008 and a maximum of 10% in the 2009).
32 preparation, however more research is needed to determine long term effects on pine species as well as evaluate additional aminocyclopyrachlor herbicide mixtures.
Introduction
Loblolly pine is native to the southeastern United States and is the most important timber species in this region (Figure 1) (Little 2006). Under well managed conditions, sawtimber-sized trees can be harvested in as little as 25 years, roughly half the time required when not managed (Cunningham et al. 2008). Urban sprawl has increased demand for timber products while reducing available land for timber production during the last century (Zhao et al. 2008). To maximize production efficiency, harvested sites must be prepared for replanting or natural regeneration by controlling weedy vegetation and preventing interference with
loblolly establishment and growth (Young et al. 2003; Britt et al. 1990).
Site preparation is the process of preparing a forestry location to encourage successful seedling establishment and is done before seedling transplant or natural regeneration. According to Young et al. (2003), there are three main objectives of site preparation: (1) to reduce competition from residual vegetation; (2) to reduce fire hazards; and (3) to prepare the seedbed by removing excess litter that could prohibit seedling establishment. In North
33 productivity estimate through a site index, associated costs, and the amount of inputs after replanting (Hamilton 1995).
DuPont Crop Protection (Wilmington, Delaware) has been developing a new herbicide with the common name of aminocyclopyrachlor which shows promise for many non-cropland uses. Aminocyclopyrachlor has a favorable environmental profile with low use rates (68 to 388 gm ai ha-1) and low mammalian toxicity, as well as a long half-life of up to 128 days (Anonymous 2009). The two forms of aminocyclopyrachlor currently undergoing registration processes are KJM44 and MAT28, with KJM44 being the more volatile and lipophilic ester formulation, while MAT28 is the less volatile free acid which KJM44 metabolizes into once absorbed. These are pyrimidine-based auxin mimic herbicides which are both soil and foliar active. With low solubility, a relatively long soil half-life, and relative broad spectrum of activity, aminocyclopyrachlor is a potentially desirable candidate for site preparation (Anonymous 2010; Bukun et al. 2010; Strachan et al. 2010).
34 Materials and Methods
A field trial was established in Mebane and Woodland, NC, during 2008 and repeated at Mebane in 2009. A randomized complete block design, split plot arrangement was used for the studies. Treatments were applied between September 10 and 20with a CO2 pressurized backpack sprayer equipped with pole sprayer to simulate an aerial spray application. Pole spray rig was equipped with a 1/4KLC-18 Fieldjet® boomless nozzle (TeeJet Technologies, Wheaton, IL) calibrated to deliver 7.5 GPA. All plots were sprayed twice in opposite
directions to ensure uniformity, coverage, and provide the desired application volume of 15 GPA. Experimental treatments included MAT28 alone (64, 128, 192, and 256, and 3.6 gm ai ha-1), MAT28 or KJM44 (128 gm ai ha-1) plus sulfometuron methyl (128gm ai ha-1) plus metsulfuron methyl (71 gm ai ha-1), and MAT28 or KJM44 (256 gm ai ha-1) plus
sulfometuron methyl (256 gm ai ha-1) plus metsulfuron methyl (71 gm ai A-1). For comparison, a standard treatment of imazapyr (566 gm ai ha-1) plus sulfometuron methyl (256 gm ai ha-1) plus metsulfuron methyl (71 gm ai ha-1) was applied. All chemical treatments also contained 1% v v-1 MSO and a non-treated control was included for comparison.
35 transplanted with a dibble planter. Pine injury, pine height, pine survival, dead pine leaders, and hardwood control was determined at 8, 9, 10, 11 and 12 MAT. The 2008 run in Mebane, was rated 25 MAT to analyze longer-term effects of pine seedlings.
All data were subjected to analysis of variance with Fisher’s Protected LSD (P≤0.05) used for mean separation using SAS version 9.1, Proc GLM (SAS 2004). The two 2008 runs were homogeneous over site locations and were pooled; the 2009 trial is presented separately.
Results and Discussion
Hardwood control. In 2008 trials at 12 MAT, hardwood control was generally similar across treatments (Table 3.1). The standard treatment of imazapyr plus metsulfuron plus sulfometuron provided 90% hardwood control, which was better than 192 or 256 gm ai ha-1 aminocyclopyrachlor. In 2009, hardwood control did not differ regardless of chemical application or rate applied with control ranging between 55 and 92% (Table 3.2).
Loblolly pine response. At 12 MAT, pine injury in 2008 trials ranged 12 to 28% with 12% winter injury observed in control plots (Table 3.1). Only the 128 gm ai ha-1 rate of
36 imazapyr plus sulfometuron plus metsulfuron plots. Aminocyclopyrachlor treatment resulted in 1.1 to 2.9 dead leaders per plot, with only KJM44 plus sulfometuron plus metsulfuron resulted in more dead leaders (2.9) than the control.
While it was expected that loblolly pine injury would decrease with greater time between aminocyclopyrachlor application and planting, this was not observed. December planting provided the least amount of pine injury (14%), had the best survival (5.3 average plant survivals per plot) and the best average height of 40 cm when compared to other months. Injury for January and February plantings were higher would typically acceptable with 20.1 to 23.2% injury and average plot survival was also statistically less with 4.2 and 3.5 average trees (Table 3.2).However, these data are not likely due to the effects of herbicide
treatments, but non-ideal planting conditions. According to North Carolina Forestry Service standards, temperature, wind, humidity, and soil conditions are essential for successful establishment of loblolly pines (Anonymous 2007). January and February planting times had average minimum air temperatures that would not provide ideal soil temperatures; in fact, some planting occurred when the ground was frozen which would inhibit establishment (Table 3.4). Furthermore, average monthly wind gust exceeded the recommendation of 10 mph or less with averages ranging between 17 and 19.15 mph (Anonymous 2011).
37 February plantings had an average of only 3.8 plants surviving, which was lower than both the December and January planting times.
Pine injury was much lower in 2009 than observed in 2008 with only 0 to 10% injury 12 MAT (Table 3.2). Also, the number alive, pine height, and number of dead leaders did not statistically differ between months or treatment. Furthermore, the number of dead leaders was not different from 2008 studies with 0.8 to 1.1 average dead leaders per plot (data not shown).
A major goal of site preparation is to control unwanted vegetation and reduce competition for light, water, and nutrients (Maier 2001; Westfall et al. 2004; Hamilton 1995). In pine
38 In addition, aminocyclopyrachlor’s application rate is also lower at a range of 68 to 388 gm ai ha-1 whereas imazapyr ranges between 560 to 1,700 gm ai ha-1 (Anonymous 2009; Senseman 2007).
40 Literature Cited
Anonymous, 2007. Pocket guide to seedling care and planting standards. North Carolina Forest Service. Sixth Edition.
Anonymous, 2009. DuPont™ DPX-MAT28 Technical Bulletin. DuPont Crop Protection. Britt, J.R., Zutter, B.R. Mitchell, R.J., Gjerstad, D.H., and Dickerson, J.F. 1990. Influence of
herbaceous interference on growth and biomass partitioning in planted loblolly pine (Pinus taeda). Weed Sci. 38: 497-503.
Anonymous. 20ll. Weather data. State Climate Office of North Carolina.
Bukun, B.,Lindenmayer, R.B., Nissen, S.J., Westra, P., Shaner, D.L., and Brunk, G. 2010. Absorption and translocation of aminocyclopyrachlor and aminocyclopyrachlor-methyl ester in Canada Thistle (Cirsium arvense). Weed Sci. 58: 96-102. Campbell, R.G. 1973. The impact of timber harvesting site preparation on selected soil
condition and plant growth. Ph.D Dissertation, University of Georgia. pp 65.
Cunningham, K., Barry, J., and Walkingstick, T. 2008. Managing loblolly pine stands…From A to Z. University of Arkansas Cooperative Extension. Available Online:
http://www.uaex.edu/Other_Areas/publications/PDF/FSA-5023.pdf. Accessed: 8
February 2011.
Hamilton, R. 1995. Reforestation as an investment: does it pay? Woodland Owner Notes. North Carolina State University Cooperative Extension. Available Online:
http://www.ces.ncsu.edu/nreos/forest/woodland/won-ob.thml. Accessed: 21 April
41 Lauer, Dwight K. and Quicke, Harold E. 2006a. Timing of chopper herbicide site
preparation relative to bedding in the establishment of lower coastal plain pine plantations. Gen. Tech. Rep. SRS-92. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. pp. 145-147.
Lauer, D.K. and Quicke, H.E. 2006b. Timing of chopper herbicide site preparation on bedded sites. South Journal of Applied Forestry. 30: 92-101
Little, E.L., 2006. Digital representations of tree species range maps from "Atlas of United States Trees". USGS. Available Online: http://esp.cr.usgs.gov/data/atlas/little/. Accessed on: 8 February 2011.
Maier, C.A. 2001. Stem growth and respiration in loblolly pine plantations differing in soil resource availability. Tree Physiology. 21: 1183-1193.
McBroom, M.W., Beasley, R.S., Chang, M. and Ice, G.G. 2008. Storm runoff and sediment losses from forest clearcutting and stand re-establishment with best management practices in east Texas, USA. Hydro. Process. 22: 1509-1522.
Mead, D.J. 2005 Opportunities for improving plantation productivity. How much? How quickly? How realistic? Biomass Bioenerg. 28:249-26.
Miller, K.V. and Miller, J.H. 2004. Forestry herbicide influences on biodiversity and wildlife habitat in southern forests. Wildelife Society Bulletin. 42: 1049-1060.
Senseman, S.A. 2007. Herbicide Handbook 9th Edition. Lawrence, KS: Weed Science Society of America.
Strachan, S.D., Casini, M.S. Heldreth, K.M., Scocas, J.A., Nissen, S.J., Bukun, B.,
42 of synthetic auxin herbicides: aminocyclopyrachlor, aminocyclopyrachlor-methyl Ester, dicamba, and aminopyralid. Weed Sci. 58: 103-108.
Rose, R. and J.S. Ketchum. 2003. Interaction of initial seedling diameter, fertilization, and weed control on Douglas-fir growth over the first four years after planting. Ann. For. Sci 60:625-635.
Wagner, R.G., K.M. Little, B. Richardson, and K. McNabb. The role of vegetation management for enhancing productivity of the world’s forests Forestry79:57-79. Westfall, J.A., Burkhart, H.E., Allen, H.L. 2004. Young stand growth modeling for
intensively-managed loblolly pine plantations in southeastern U.S. Forest Science. 50: 823-835.
Young, R.A. and Giese, R.L. 2003. Introduction to forest ecosystem science and management. Third Edition.
44 Table 3.1. Evaluation of loblolly pine site preparation treatments with aminocyclopyrachlor and industry standards for hardwood control and pine response from 2008 trials at one year after treatment.
Rate Hardwood
controlb Pine Injuryb Pine Survivalc Pine Heightd Dead Leadere
Treatmenta gm ai ha-1 % % No. (cm) No.
MAT28 64 66 ab 24 ab 4.3 ab 35 ab 1.2 b
MAT28 128 66 ab 28 a 3.6 ab 30 b 1.4 ab
MAT28 192 58 b 19 ab 4.4 ab 33 ab 1.7 ab
MAT28 256 58 b 19 ab 4.9 a 39 a 2.1 ab
KJM44 + sulfometuron methyl + metsulfuron methyl
128 + 212
+ 71 65 ab 16 b 4.8 a 37 ab 2.9 a
KJM44 + sulfometuron methyl + metsulfuron methyl
256 + 128/
+ 71 70 ab 15 b 4.6 ab 33 ab 1.7 ab
MAT28 + sulfometuron methyl + metsulfuron methyl
128 + 128
+ 128 69 ab 22 ab 4.4 ab 36 ab 1.1 b
MAT28 + sulfometuron methyl + metsulfuron methyl
256 + 212
+\ 212 74 ab 22 ab 4.1 ab 39 a 1.9 ab
Imazapyr + sulfometuron methyl + metsulfuron methyl
566 + 212
+ 71 90 a 13 b 4.8 a 38 ab 0.7 b
Control -- -- 12 b 3.3 b 341 ab 0.7 b
aAll chemical treatments contained 1% v v-1 MSO. b
Control rated a 0 to 100% scale; 0 being no control, 100 being complete plant death .
cPine survival equals the average survival per treatment across all plots. dHeight equals the average height per treatment across all plots.
eDead leader equals the average number of dead/split auxiliary terminals per treatment across
all plots.
fMeans within column followed by the same letter are not statistically different based upon
45
46 Table 3.3. Pine injury, survival, and height data pooled over
treatments and segregated by month at one and two years after treatment.a,b.c
Injury Survival Height
% No. cm
Month 1YAT
December 14 b 5.3 a 40 a
January 20 ab 4.2 b 34 b
February 23 a 3.5 b 32 b
2 YAT
December 0 a 5.5 a 105 a
January 0 a 6.4 a 105 a
February 0 a 3.8 b 100 a
aPine injury rated a 0 to 100% scale; 0 being no injury, 100 being
complete plant death.
bPine survival equals the average survival per treatment across all plots. cHeight equals the average height per treatment across all plots. d
47 Table 3.4. Weather data indicating the average daily temperature, wind gust, and minimum temperature at the three planting times (Anonymous 2011).
Planting Month
Average Daily Temp
Average Minimum
Temp
Average Daily Wind Gust
Monthly Precipitation
c c Km/h cm
2008 Runs
Dec 9.3 3.9 37.5 7.8
Jan 15.8 5.7 27.4 6.5
Feb 7.3 1.5 30.8 4.2
2009 Run
Dec 4.8 -3.3 43.1 15.5
Jan 3.1 -2.6 36.8 17.4
48 Chapter IV
Absorption, Translocation, and Metabolism of Aminocyclopyrachlor in Loblolly Pine (Pinus taeda)
Abstract
Greenhouse and laboratory experiments were conducted using 14C-aminocyclopyrachlor to evaluate root and foliar absorption, translocation, and metabolism in loblolly pine. Pine seedling plugs were used for all experiments. Trees designated for foliar experiments were first treated with formulated aminocyclopyrachlor in an overhead track sprayer before application of radiolabeled aminocyclopyrachlor to a single pine needle. Trees for root absorption studies were grown in half strength Hogland’s solution spiked with 14 C-aminocyclopyrachlor. Plants were harvested at 1, 2, 4, 8, 24, and 48 hours after treatment (HAT) for all experiments. Plants with foliar treatments were harvested and divided into roots, lower stem, upper stem, bud, treated pine needle with fascicle, and untreated pine needle(s). Plants treated by root application were harvested and divided into roots, lower stem, upper stem, and bud. All partitioned plant parts were stored at -20C. To determine absorption and translocation, designated plant parts were dried, homogenized, and radiation was quantified using liquid spectroscopy after being combusted in a biological oxidizer. Aminocyclopyrachlor metabolism was determined only in the treated needle and fascicle. The tissue was extracted in 90% methanol, and evidence of metabolism was determined using High Performance Liquid Chromatography. A maximum of 37% of
49 with maximum reached by one hour after treatment. No difference was found in translocation regardless of harvest interval; 59% of the free acid remained within the treated needle and fascicle, 27% remained in the upper stem section, and all other parts had significantly less aminocyclopyrachlor with a range of 0.5 to 9%. Root absorption occurred in a linear fashion at a rate of one percent per hour and showed high xylem mobility after 48 HAT. Lastly, no metabolism of aminocyclopyrachlor free acid was seen between 1 and 48 HAT when foliar applied.
Introduction
Loblolly pine is indigenous to the southeastern United States (Figure 4.1; Little 2006). It is the most important timber species in this region, growing on more than 100 million acres. This region is also favorable to many brush species that must be managed to prevent
interference with loblolly pine growth and harvest (Monaco 2002). Numerous herbicides are available for weed control in silviculture settings. For site preparation prior to planting, herbicide options include glyphosate, hexazinone, imazapyr, metsulfuron, sulfometuron, and triclopyr. However, not all of these are safe to loblolly pine after planting has occurred.
50 structure is similar to both aminopyralid and clopyralid, with the exception of an additional nitrogen atom and cyclopropyl side chain (Figure 4.2; Bukun 2010). Among its advantageous properties, it has a favorable environmental profile, low use rates (68 to 388 gm ai ha-1), low mammalian toxicity, and a long half-life of up to 128 days.
Currently only two papers have been published regarding absorption and translocation of aminocyclopyrachlor and its free acid (fa). Bukun et al. (2010) found a 27% greater absorption rate with the methyl ester formulation in comparison to the fa in Canada thistle (Cirsium arvense), which is consistent with prickly lettuce (Lactuca serriola L.), rush skeletonweed (Chondrilla juncea L.), and yellow starthistle (Centaurea solstitialis L.) as reported by Bell et al. (2011). Both the methyl ester and free acid were rapidly absorbed and reached maximum absorption within the first 24 hours. These results suggest that
aminocyclopyrachlor methyl ester is advantageous for absorption, but is rapidly metabolized due to de-esterification. Low translocation percentages were found with both
aminocyclopyrachlor formulations in below ground biomass indicating poor phloem mobility likely due, in part, to the low log octanol-water partition coefficient (Kow) (Bukun et al. 2010; Hsu and Kleier 1996).
Past research by Roten et al. (2009) found volunteer loblolly pines to be sensitive to aminocyclopyrachlor with injury up to 80%, but pines transplanted after application were more tolerant and injury did not exceed 20%. These findings, coupled with
51 translocation, or metabolism may be factors in transplanted loblolly pine tolerance.
Therefore, research was conducted to determine absorption, translocation, and metabolism of aminocyclopyrachlor-fa in loblolly pine and further assess its potential use in pine
plantations.
Materials and Methods
Plant material. Third generation, premium loblolly pine plugs were purchased from the North Carolina Division of Forestry Resources (Goldsboro, NC). To prepare plants for root absorption, translocation, and metabolism studies, the roots were washed to remove debris. Directly after cleansing, individual trees were placed in 250 mL Erlenmeyer flasks
containing 220 mL half strength Hoagland’s Solution. These plants were given 24 hours to acclimate before treatment. To prepare plants for foliar absorption, translocation, and metabolism studies, they were planted in 15 cm pots filled with sterilized sand and given 48 hours to acclimate before treatment. Studies were conducted in a greenhouse at the North Carolina State University Weed Control Labs with natural day light and temperature setting of 21 ± 4 C in October 2010.
Root absorption and translocation. Plants of similar size were segregated into replicates and removed from flasks. Flasks were then drained and refilled with 220 ml half strength Hoagland’s solution with 8.4 kBq 14
52 Plants were harvested at 1, 2, 4, 8, 24, and 48 hours after treatment. At harvest, roots were washed with 30mL 50:50 methanol and water to remove any remaining radiation. Plants for the absorption and translocation study were partitioned into roots, lower stem, upper stem, and terminal bud. All sections or trees were individually placed in coin envelopes and stored in the freezer at -20 C for later processing.
Foliar Absorption and Translocation. In preparation for these experiments, the tip of a central pine needle was painted with an orange acrylic paint for indication of treatment site. Trees for this experiment were then treated with formulated aminocyclopyrachlor in a single-nozzle, overhead track sprayer calibrated to deliver 250 gm ai ha-1 at a 140 L ha-1 application rate. To ensure timely application of radiolabeled spotting, one replicate at a time was sprayed then brought to the greenhouse. Immediately after introduction to the greenhouse, 10µL of a treatment solution containing 4.2 kBq of 14C aminocyclopyrachlor were administered to the designated pine needle. Each application time was recorded for
harvesting purposes. The same spotting solution was used as before except one percent v v-1 MSO was added.
53 seconds in a 20mL scintillation vial containing 5mL, 50:50 methanol:water to remove excess radiation not absorbed into plant tissue. Harvested portions included roots, lower stem, upper stem, terminal bud, treated needle and fascicle, and untreated needle(s). All material was then placed in individual envelopes and then immediately frozen and stored at -20C for later processing.
Absorption and translocation analysis. Plant material from the foliar and root absorption and translocation studies were oven dried at 60 C for 72 h. Individual sections were
homogenized with a commercial grade blender1; blender was cleansed using radiation removal towelettes between sample sections to avoid contamination. Samples were then weighed, recorded, and a 0.05 gram subsample was placed in a 1.5 inch ashless filter paper for combustion in a biological oxidizer2; if sample was less than 0.05 g, the sample was burned in its entirety. Radioactivity was trapped in 15 ml of 14C trapping cocktail3 quantified using liquid spectroscopy4 (LSS).
54 the glass beads and biomass pellet was placed onto a 3.8 cm asheless filter paper, air dried and then oxidized and quantified by LSS.
The supernatant of the samples were dried under N2 and resuspended with 1.5 mL 90:10 methanol:water plus 0.05% v v-1 phosphoric acid obtain uniform sample sizes. Samples were then filtered with a 0.45 µm filter. To determine if there was metabolism of
aminocyclopyrachlor, the samples were subjected to high-performance liquid
chromatography (HPLC). The extracted samples were compared with unlabeled technical and radiolabeled 14C aminocyclopyrachlor. The HPLC system included a gradient pump6, a UV absorbance7 detector set at 254 nm, and a 14C radiation detector8 with a 250µL liquid cell. The solid phase was a 250mm x 4.6mm i.d., Adsorbosphere C18 5 micron column9. The samples were separated with a gradient, with of mobile phases consisting of (A) 99.9% ultra-pure water : 0.01% acetonitrile plus 0.05% v v-1 formic acid, (B) 50% ultra-pure water : 50% acetonitrile plus 0.05% v v-1 formic acid. The separation program included: 10 min column equilibration with A; followed by a linear gradient for 10 min from 100% A to 100% B; then further elution with B for 10 minutes; and a column wash with 100% methanol for 10
minutes. Methanol, water, and formic acid were HPLC grade.
55 compared over time in contrast statements using SAS PROC MIX and means were compared using Fisher’s Protected LSD (P ≤ 0.05) (SAS 2004). To determine metabolism of
aminocyclopyrachlor, radioactivity profile from the treated samples was compared to the profile from the standard. The retention time (rt) of the 14C-aminocyclopyrachlor standard was 8 min, which was the same as the rt of the unlabeled standard when monitored with the UV detector.
Results and Discussion
Foliar applied absorption and translocation. No differences were found in the amount of aminocyclopyrachlor absorption based on harvest time. Rapid absorption was observed in the first hour (37%) and only increased 8%, respectively over the experimental time course (Figure 4.3). Translocation P-values indicate that there were no interactions between runs or harvest intervals. Therefore, all data were pooled by harvested plant parts. The majority of absorbed 14C-aminocyclopyrachlor (59%) remained within the treated needle and fascicle (Table 4.1). This absorption was significantly greater than 14C recovered in the stem top (27%), which was also greater than all other harvested plant parts. Translocation to the stem bottom, untreated needle(s), bud, and root sections were similar with 0.5 to 9% of the absorbed herbicide found in these plant parts.
56 first 24-h. Aminocyclopyrachlor-fa absorption in loblolly pine seedlings (37%) was 20% less than foliar absorption in Canada thistle (Cirsium arvense) (Bukum et al., 2010). Though there was less absorption in pine seedlings, much more of the herbicide stayed within the treated needle (59% at 48 h) whereas Bukun et al. (2010) found only 2.8% in the treated leaf of Canada thistle after 192 h.
Root absorption and translocation. When root applied, 14C-aminocyclopyrachlor absorption ranged from 1 to 8% between 1 and 8 HAT (Figure 1). At 24 and 48 HAT,
absorption increased to 21 and 47%, respectively. This absorption demonstrated greater total herbicide absorption when root applied than when foliar applied, but absorption was much slower. Translocation was similar to absorption with increased herbicide movement and accumulation in different plant sections over time. Few differences in translocation were observed between 1 and 8 HAT (Figure 4.4). However, at 24 HAT, increased translocation was observed with 50,000 dpm in the stem top. At 48 HAT, approximately 100,000 dpm were found in the stem tops and 30,000 dpm in the partitioned pine buds.
Metabolism. Only the treated needle and fascicle were studied in the metabolism trial
58 Sources of Materials
1
Waring Blender 7011, model 3113L92, 314 Ella T. Grasso Avenue Torrington, CT 06790
2
Model OX-500 Biological Material Oxidizer, R. J. Harvey Instrument Corp., 123 Patterson Street, Hillsdale, NJ 07642.
3
Carbon 14 cocktail, R.J. Harvey Instruments Corp., 123 Patterson Street, Hillsdale, NJ 0764211
4
Packard TRI-CARB 2100TR Liquid Scintillation Spectrometer,
Packard Instrument Company, 2200 Warrenville Road, Downers Grove, IL 60515. 5
Silamat S5, Ivacar Vivadent, 175 Pineview Dr., Amherst, NY 14228. 6
L-6200A Intelligent Pump. Hitachi. Japan. 7
Waters 486 Tunable Absorbance Detector. Waters Corp., 34 Maple St., Milford, MA., 01757.
8
Flo-one® Beta Radiomatic Flow Scintillation Analayzer. Packard Instrument Company, 2200 Warrenville Road, Downers Grove, IL 60515.
9
59 Literature Cited
Anonymous, 2009. DuPont™ DPX-MAT28 Technical Bulletin. DuPont Crop Protection. Bell, J.L., Burke, I.C., and Prather, T.S. 2011. Uptake, translocation, and metabolism of
aminocyclopyrachlor in prickly lettuce, rush skeletonweed, and yellow starthistle. Pest Management Science. 67: 1338-1348.
Bukun, B., Gains, T.A., Nissen, S.J., Westra, P., Brunk, G., Shaner, D.L., Sleugh, B.B., and Peterson, V.F. 2009. Aminopyralid and clopyralid absorption and translocation in Canada Thistle (Circium arvense). Weed Sci. 57: 10-15.
Bukun, B.,Lindenmayer, R.B., Nissen, S.J., Westra, P., Shaner, D.L., and Brunk, G. 2010. Absorption and translocation of aminocyclopyrachlor and aminocyclopyrachlor-methyl ester in Canada Thistle (Cirsium arvense). Weed Sci. 58: 96-102.
Little, E.L., 2006. Digital Representations of Tree Species Range Maps from "Atlas of
United States Trees". USGS. Available Online: http://esp.cr.usgs.gov/data/atlas/little/. Accessed on: 8 February 2011.
Monaco, T.J., Weller, S.C., ND Ashton, F.M. 2002. Weed Science. Principles and Practices. John Wiley and Son, inc. New York. 351.Roten, R.L. Richardson, R.J., Gardner, A.P. Response of Selected Woody Plants to DPX-KJM44. Abstract 218 in Proceedings of the 49th annual WSSA meeting in Orlando, FL. Champaign, IL: Weed Science Society of America.
62
63 Table 4.1 Translocation of foliar applied 14C-aminocyclopyrachlor and percentage of
absorbed recovered per plant part.
Plant part DPM % Recovered
Treated needle w/ fascicle 54,305 A 59%
Upper stem 25,056 B 27%
Lower stem 8,079 C 9%
Untreated needle(s) 2,899 C 3%
Roots 1,724 C 2%
64 Figure 4.3. Foliar and root absorption of aminocyclopyrachlor during a 48-h span.
66 Figure 4.5. HPLC chromatograms illustrating a typical treated and processed
